Remarks

Using the -= operator is exactly the same as doing the following:

result = result - expression

The -= operator is the arithmetic subtraction operator used to find the difference between two numbers.

As for all arithmetic operators, JScript will generate runtime errors for every case in the table below where an E is indicated:

	obj	as	ns	num	bool	undef	null
obj	N	E	N	N	N	E	E
as	E	E	E	E	E	E	E
ns	N	E	N	N	N	E	E
num	N	E	N	N	N	E	E
bool	N	E	N	N	N	E	E
undef	E	E	E	E	E	E	E
null	E	E	E	E	E	E	E

obj = Object, as = Alphanumeric String, ns = Numeric String, num = Number, bool = Boolean, undef = Undefined, null = Null value.